1. Field of the Invention
This invention relates to modified colored pigments, such as modified carbon products, and ink jet inks, inks and coatings which contain modified colored pigments. The present invention is further directed to ink compositions and, more particularly, to aqueous ink compositions suitable for imaging applications, such as ink jet printing processes.
2. Discussion of the Related Art
Presently, predominant black pigments are carbon blacks which can be used as colorants either in dry, powdered form, a flushed paste, or a liquid dispersion form depending upon the method to apply the pigment to the substrate and the substrate requirements. Generally, physical and surface properties of the colorant influences the hue, permanency, bulk, opacity, gloss, rheology, end use, and print quality.
There are various classifications of inks used presently. These categories include printing inks, ultraviolet cure inks, ball-point inks, and stamp pad or marking inks. Generally, inks can be applied by letter press, lithographic, flexographic, gravure, silk screen, stencil, duplicating, and electrostatic. Inks thus can be found in such end uses as news, publication, commercial, folding carton, book, corrugated box, paper bag, wrapper, label, metal container, plastic container, plastic film, foil, laminating, food insert, sanitary paper, textile and the like. McGraw-Hill's Encyclopedia of Science and Technology, Vol. 7, pgs. 159-164, provides further details of the types of inks available and their uses, all of which is incorporated herein by reference.
Coatings can contain pigments as well and are used for decorative, protective, and functional treatments of many kinds of surfaces. These surfaces include, coils, metals, appliances, furniture, hardboard, lumber and plywood, marine, maintenance, automobile, cans, and paperboard. Some coatings, such as those on undersea pipelines, are for protective purposes. Others, such as exterior automobile coatings, fulfill both decorative and protective functions. Still others provide friction control on boat decks or car seats. Some coatings control the fouling of ship bottoms, others protect food and beverages in cans. Silicon chips, printed circuit panels, coatings on waveguide fibers for signal transmission, and magnetic coatings on video tapes and computer disks are among many so-called hi-tech applications for coatings.
Categories of aqueous vehicles for aqueous inks and coatings include those in which the binder is soluble in water, those in which it is colloidally dispersed, and those in which it is emulsified to form a latex. The combination of binder and volatile liquid is called the vehicle which may be a solution or a dispersion of fine binder particles in a non-solvent. Pigments are finely divided, insoluble, solid particles dispersed in the coating vehicle and distributed throughout the binder in the final film. Surfactants or polymers can be used as pigment dispersants. The components and manufacturing of aqueous coatings are further discussed in the Concise Encyclopedia of Polymers, Science and Engineering, pgs. 160-171 (1990), which is incorporated herein by reference.
Non-aqueous inks and coatings are used for many applications in which aqueous vehicles are not suitable. For instance, inks which are to be printed on hydrophobic, non-porous substrates such as metal, glass, or plastics must be fast-drying. Therefore, solvents such as ketones, esters, alcohols, or hydrocarbons are often used instead of water. Such solvent-based inks are used widely for industrial labeling of cardboard boxes and various metal or plastic containers and components. Specific examples include news ink compositions and web off-set gloss heat-set ink compositions.
Inks and coatings are also required to be water resistant in certain situations. In such instances, water-resistant resins can be dissolved in non-aqueous solvents of ink and coating formulations to provide the desired water resistance upon drying. A primary use of such non-aqueous coatings is on metal and plastic automotive parts.
Ink jet printing is a non-impact process wherein droplets of ink are produced and deposited on a substrate such as paper, transparent film, polymer sheet, or textile material in response to an electronic signal. Ink jet printing systems are typically classified by two known types: continuous stream or drop-on-demand.
Ink compositions which are useful in imaging applications, such as ink jet ink printing systems, are well known and generally contain water soluble dyes. Although dye-based inks are suitable for their intended purposes, dyes have several disadvantages when used in ink jet inks. For examples, dyes, being water-soluble in a water/organic mixture, may dissolve and run when exposed to moisture or water. Dye images may further smear or rub off on contact with felt pen markers or upon being rubbed or touched by finger. Dyes also exhibit poor light stability when exposed to visible, ultraviolet light, or sunlight.
Pigments are also known as colorants in ink compositions but have not received a wide degree of acceptance in ink jet ink systems, for example, because of problems associated with the performance and reliability of the composition, i.e., print properties, stability, latency, and the like.
As a result, although known compositions are suitable for their intended purpose, a need remains for improved ink compositions, especially for use in the ink jet printers, which overcome the problems typically associated with current dye-based and pigment systems. In addition, there is a need for improved ink compositions providing good print properties and generating printed images having improved waterfastness.